Process of Producing a Cellulosic Fibre Web

ABSTRACT

The present invention relates to a process of producing a cellulosic fibre web comprising a) providing a cellulosic suspension to which a debonder system can be added, b) dewatering the cellulosic suspension and forming a cellulosic fibre web, and c) applying a smectite clay to said cellulosic fibre web with or without adding a polymer in an amount from about 0.01 to about 2 kg/t dry cellulosic fibres. The invention also relates to a web obtainable by the process.

The invention relates to a process of producing a cellulosic fibre webwhich may be further processed to air-laid paper, tissue or fluff. Theinvention also relates to a cellulosic fibre web obtainable from theprocess and air-laid paper, tissue, or fluff obtainable by furtherprocessing of the cellulosic fibre web.

BACKGROUND OF THE INVENTION

When manufacturing paper, especially air-laid paper, tissue and fluff,static electricity, measured as static potential, can be a problem. Itcan cause discharges or sparks, which disturb the production.Furthermore, if the dry fibres have a high static potential the fibrestend to glue themselves to process equipment such as mills, defiberizersand pipes. The fibres are accumulated and discharged as big lumps whichcreate problems when forming the end product. Since the formation of theproduct usually is made from dry fibres, an even distribution of thefibres is important and lumps of fibres should be avoided. In theproduction of air-laid paper, uncontrolled static potential can resultin extensive dusting which in turn can result in dust explosions.Attempts to reduce the static potential can also lead to deteriorationof debonding agents, which may be added to enhance the softness of theproduct by interfering with natural fibre-to-fibre bonds that occurduring sheet formation in the papermaking process.

WO 2007/058609 discloses a process in which the static potential of thefibres/paper product can be controlled and reduced while enhancing thesoftness of the produced paper product. However, it is desirable tofurther control the static potential. Also, it is desirable to obtainuniform spreading/dispersion of an antistatic agent. A further object isto increase the retention and effective use of an antistatic agent.

It is a further object of the present invention to provide a processthat can considerably reduce the static potential by a small dosage ofan antistatic agent without need of further additives.

According to one embodiment of the invention, it is a further object ofthe present invention to provide a papermaking process that can controlthe static potential while maintaining adequate softness of the product.

THE INVENTION

The present invention relates to a process of producing a cellulosicfibre web comprising

a) providing a cellulosic suspensionb) dewatering the cellulosic suspension and forming a cellulosic fibrewebc) applying a smectite clay in an amount from about 0.01 to about 2 kg/tdry cellulosic fibres to said cellulosic fibre web,wherein no polymer is added to the formed cellulosic fibre web.

The present invention also relates to a process of producing acellulosic fibre web comprising

a) providing a cellulosic suspension and adding a debonder system to thecellulosic suspensionb) dewatering the cellulosic suspension and forming a cellulosic fibrewebc) applying a smectite clay in an amount from about 0.01 to about 2 kg/tdry cellulosic fibres to said cellulosic fibre web.

The term “cellulosic fibre web” as used herein, includes any sheet orweb prepared from cellulosic fibres such as pulp sheets or paper webs.

It has been found addition of smectite clay to a formed cellulosic fibreweb prevents interaction of smectite with components present in thecellulosic suspension which may disturb the intended purpose, i.e. toprovide controlled antistatic effect.

According to one embodiment, the smectite clay is added to the formedweb in an amount from about 0.1 to about 2, for example from about 0.1to about 1, or from about 0.1 to about 0.75, or from about 0.1 to about0.5, or from about 0.1 to 0.25 kg/ton dry cellulosic fibres. Accordingto one embodiment, smectite clay is added to the formed web in an amountfrom about 0.25 to about 0.75 kg/ton dry cellulosic fibres. According toone embodiment, the smectite clay is present in an aqueous dispersion.According to one embodiment, the smectite clay, for example indispersion form, is sprayed on the web.

According to one embodiment, smectite clays which can be used accordingto the present invention include for example montmorillonite/bentonite,hectorite, beidelite, nontronite, saponite, and mixtures thereof.According to one embodiment, the smectite clay is laponite and/orbentonite.

According to one embodiment, the smectite clay can be modified e.g. byintroducing a cation or a cationic group, such as a quaternary ammoniumgroup or an alkali metal, for example lithium.

According to one embodiment, the smectite clay is a synthetic hectoriteclay modified with lithium. This clay is sold under the name Laponite®from Rockwood or Eka Soft F40 from Eka Chemicals AB. Examples of suchclays, and the manufacturing of such clays, include those disclosed inWO 2004/000729. The smectite clay used according to the presentinvention can have a specific surface area from about 50 to about 1500,for example from about 200 to about 1200, or from about 300 to about1000 m²/g. Suitable products may be for example Bentonite fromSud-Chemie, BASF and Clayton; Bentolite (Bentonite) from Southern ClayProducts; and Hydrotalcite from Akzo Nobel.

According to one embodiment, the smectite clay can be applied byimmersion of the cellulosic fibre web into a solution or dispersion ofthe smectite clay.

The aqueous dispersion of smectite clay can either be produced inadvance or dispersed on site. According to one embodiment, the smectiteclay is added as a powder.

According to one embodiment, no further component is added separately orin conjunction with smectite clay to the formed cellulosic fibre web.

According to one embodiment, smectite clay is also added to thecellulosic suspension, for example in an amount of from about 0.01 toabout 10, such as from about 0.05 to about 5, or from about 0.1 to about2 or from about 0.25 to about 1 kg/ton dry cellulosic fibres.

According to one embodiment, the weight ratio of smectite clay added tothe cellulosic suspension and smectite clay added to the cellulosicfibre web ranges from about 1:100 to about 100:1 for example from about5:95 to about 80:20, or from about 10:90 to about 50:50, or from about15:85 to about 40:60 or from about 20:80 to about 30:70.

According to one embodiment, a debonder system such as a debondercomposition is added to the suspension. Whereas a debonder compositionmay comprise one or several components in a mixture which is addedjointly or in conjunction to the cellulosic suspension, a debondersystem may also involve one or several components which are addedseparately to the cellulosic suspension.

According to one embodiment, a debonder system is added as a pre-mixedemulsion further comprising a polymer as defined herein.

According to one embodiment, the weight ratio of the debonder system tosmectite clay ranges from about 1:50 to about 100:1, for example fromabout 1:10 to about 50:1 or from about 1:5 to about 20:1, or from about1:2 to about 10:1, or from about 1:1 to about 5:1.

According to one embodiment, the debonder system comprises

(i) an oil, fat or wax,(ii) at least one non-ionic surfactant, and(iii) at least one anionic surfactant

According to one embodiment, the debonder system comprises at least onequaternary ammonium surfactant.

According to one embodiment, refined and/or hydrogenated grade oils, forexample vegetable oils like grape oil, olive oil, coconut oil, rape seedoil, sunflower oil and palm oil, for example coconut oil is comprised inthe debonder system.

According to one embodiment, mineral oils and/or silicon oil arecomprised in the debonder system.

According to one embodiment, the debonder system is free orsubstantially free from quaternary ammonium surfactants. By“substantially free” is meant that quaternary ammonium surfactantsconstitute less than 5 wt %, for example less than 1, or less than 0.5wt % of the total amount of the debonder system.

According to one embodiment, the debonder system, i.e. the total amountof component(s) making up the system, is added in an amount from about0.1 to about 10, for example from about 0.3 to about 7, or from about0.5 to about 5 kg/ton dry cellulosic fibres.

According to one embodiment, to avoid deterioration of the differentadditives, a preserving agent may be added. Several cosmetic additivescan also be included, for example antioxidants, e.g. tocopherol, andaloe vera.

According to one embodiment, the cellulosic fibre web is furtherprocessed to produce air-laid paper, tissue or fluff. According to oneembodiment, the paper produced is not printing paper or cardboard and/orpaperboard.

The present invention also relates to a cellulosic fibre web obtainableby the process as described herein.

The present invention also relates to a cellulosic fibre web comprisingsmectite clay in an amount from about 0.25 to about 0.75 kg/ton drycellulosic fibres wherein the static potential is lower than 5 kV.

According to one embodiment, the static potential of the cellulosicfibre web is lower than 10, or lower than 8, or lower than 6, or lowerthan 5 kV.

According to one embodiment, the defiberization energy of the cellulosicfibre web is lower than 120, such as lower than 110 or lower than 100kJ/kg.

According to one embodiment, less than 10, for example less than 5 orless than 1 wt % of colloidal silica particles based on the weight ofsmectite clay are added to the formed cellulosic fibre web. According toone embodiment, no colloidal silica particles are added to the formedcellulosic fibre web. According to one embodiment, no or substantiallyno organophilic compound such as organophilic smectite or organophilicsilicate is added to the formed cellulosic fibre web. According to oneembodiment, no or substantially no quarternary organic ammonium compoundis added to the web. According to one embodiment, no or substantially nostarch compound is added to the web.

According to one embodiment, colloidal silica particles are added to theformed cellulosic fibre web in an amount from about 0.01 to about 50,for example from about 0.02 to about 20, or from about 0.05 to about 10,or from about 0.1 to about 5 or from about 0.125 to about 2 or fromabout 0.25 to about 1 kg/ton dry cellulosic fibres.

According to one embodiment, the cellulosic fibre web has a dry contentof from about 5 to about 99, for example from about 25 to about 95 orfrom about 50 to about 95 or from about 65 to about 95 or from about 80to about 95 wt % based on the total weight of the web.

According to one embodiment, the cellulosic fibre web has a dry contentfrom about 20 to about 70, for example from about 30 to about 60 or fromabout 35 to about 50 wt % based on the total weight of the web.

According to one embodiment, at least one polymer such as non-ionic,amphoteric, and/or cationic polymers or mixtures thereof can be added tothe cellulosic suspension, in particular polymers which are highlycharged. The polymer can be derived from natural or synthetic sourcesand can be linear, branched or cross-linked, e.g. in the form ofparticles. According to one embodiment, the polymer is water-soluble orwater-dispersible.

Examples of suitable cationic polymers include cationic polysaccharides,e.g. starches, guar gums, celluloses, chitins, chitosans, glycans,galactans, glucans, xanthan gums, pectins, mannans, dextrins. Suitablestarches include potato, corn, wheat, tapioca, rice, waxy maize, barley,etc. Cationic synthetic organic polymers such as cationic chain-growthpolymers may also be used, e.g. cationic vinyl addition polymers likeacrylate-, acrylamide-, vinylamine-, vinylamide- and allylamine-basedpolymers, for example homo- and copolymers based on diallyldialkylammonium halide, e.g. diallyldimethyl ammonium chloride, as well as(meth)acrylamides and (meth)acrylates. Further polymers include cationicstep-growth polymers, e.g. cationic polyamidoamines, polyethyleneimines, polyamines, e.g. dimethylamine-epichlorhydrin copolymers, andpolyurethanes. Further examples of suitable cationic organic polymersinclude those disclosed in WO 02/12626.

According to one embodiment, the polymer is selected from the group ofpolydiallyldimethyl ammonium chloride, polyamines, cationic starch,amphoteric starch, and polyamidoeamine-epichlorohydrin (PAAE),polyethylene imines and polyvinylamines.

The term “step-growth polymer”, as used herein, refers to a polymerobtained by step-growth polymerization, also being referred to asstep-reaction polymer and step-reaction polymerization, respectively.The term “chain-growth polymer”, as used herein, refers to a polymerobtained by chain-growth polymerization, also being referred to as chainreaction polymer and chain reaction polymerization, respectively.

According to one embodiment, the polymer has a molecular weight of fromabout 10000 to about 10000000, for example from about 15000 to about5000000, or from about 40000 to about 1000000 g/mol.

According to one embodiment, an anionic polymer such as anionicstep-growth polymers, chain-growth polymers, polysaccharides, naturallyoccurring aromatic polymers and modifications thereof is added to thecellulosic suspension.

According to one embodiment, the total amount of polymer added rangesfrom about 0.01 to about 10, such as from about 0.1 to about 5 or fromabout 0.2 to about 2 kg/ton dry cellulosic fibres.

According to one embodiment, an aqueous solution containing the polymeris prepared in which the polymer content is from about 0.1 to about 50,such as from about 0.5 to about 25 wt % which subsequently is added tothe cellulosic suspension.

According to one embodiment, the aqueous polymer solution is heated upto about 20 to about 70, for example up to about 25 to about 55° C.According to one embodiment, an emulsion of an emollient-surfactantblend and an aqueous solution containing the polymer is prepared with, astatic mixer, a high shear device called ultra-turrax or a homogenizer.The emulsion can then be cooled to room temperature. The cooling can beperformed for example by means of a heat exchanger.

According to one embodiment, an anionic surfactant and/or anionicmicroparticles such as anionic silica particles, for example anioniccolloidal silica particles, smectite clays, or mixtures thereof areadded to the cellulosic suspension.

According to one embodiment, the anionic colloidal silica particles asdefined herein are hydrophobically modified.

Colloidal silica particles which can optionally be added to thecellulosic suspension and/or the cellulosic fibre web may be derivedfrom e.g. precipitated silica, micro silica (silica fume), pyrogenicsilica (fumed silica) or silica gels with sufficient purity, andmixtures thereof. According to one embodiment, the silica particles aresilanised as described in W02004/035474. The silica sol may also,typically, be produced from waterglass as raw material as disclosed ine.g. U.S. Pat. No. 5,368,833.

Colloidal silica particles and silica sols according to the inventionmay be modified and can contain other elements such as amines, aluminiumand/or boron, which can be present in the particles and/or thecontinuous phase. Boron-modified silica sols are described in e.g. U.S.Pat. No. 2,630,410. The aluminium modified silica particles suitablyhave an Al₂O₃ content of from about 0.05 to about 3 wt %, for examplefrom about 0.1 to about 2 wt %. The procedure of preparing an aluminiummodified silica sol is further described in e.g. “The Chemistry ofSilica”, by Iler, K. Ralph, pages 407-409, John Wiley & Sons (1979) andin U.S. Pat. No. 5,368,833.

The colloidal silica particles suitably have an average particlediameter ranging from about 2 to about 150, for example from about 3 toabout 50, or from about 5 to about 40 nm. Suitably, the colloidal silicaparticles have a specific surface area from about 20 to about 1500, forexample from about 50 to about 900, or from about 70 to about 600 m²/g.

According to one embodiment, anionic surfactants that can be usedaccording to the invention are for example anionic surfactants withhydrophobic “tails” having from about 6 to about 30 carbon atoms.Examples of anionic surfactants are saponified fatty acids,alkyl(aryl)sulphonates, sulphate esters, phosphate esters,alkyl(aryl)phosphates, alkyl(aryl) phosphonates, fatty acids,naphthalene sulphonate (NAS), formaldehyde polycondensates, polystyrenesulphonates, hydrophobe-modified NAS, for example saponified fattyacids, alkyl(aryl)sulphonates, sulphate esters, phosphate esters,alkyl(aryl)phosphates, alkyl(aryl) phosphonates, and mixtures thereof.

According to one embodiment, the anionic surfactant and/or anionicmicroparticle is added to the cellulosic suspension in a total amountfrom about 0.001 to about 1, such as from about 0.005 to about 0.5, orfrom about 0.01 to about 0.1 kg/ton dry cellulosic fibres.

According to one embodiment, non-ionic surfactants that can be usedaccording to the invention include generally ethoxylated or propoxylatedfatty acids or fatty alcohols. The ethoxylated fatty acids and fattyalcohols can be ethoxylated with from about 1 to about 30 ethylene oxide(EO), or from about 4 to about 25 EO. The ethoxylated fatty acids andfatty alcohols may have from about 6 to about 30 carbon atoms, or fromabout 6 to about 22 carbon atoms. The propoxylated fatty acids and fattyalcohols may have been propoxylated with from about 1 to about 30propylene oxide (PO), or from about 1 to about 8 PO. The propoxylatedfatty acids and fatty alcohols can have from about 6 to about 30 carbonatoms, such as from about 6 to about 22 carbon atoms. It is alsopossible to use carbon dioxide instead of propylene oxide.

According to one embodiment, a non-ionic surfactant is added in anamount from about 0.1 to about 10, for example from about 0.3 to about7, or from about 0.5 to about 5 kg/ton dry cellulosic fibres.

According to one embodiment, further conventional components may beadded to the cellulosic suspension such as wet strength agents, drystrength agents and wetting agents.

According to one embodiment, the cellulosic fibres of the cellulosicsuspension may include fibres derived from wood pulp, which includeschemical pulp such as, sulphite and sulphate pulps, as well asmechanical pulps such as ground wood, thermomechanical pulp and chemicalmodified thermomechanical pulp. Recycled fibres may also be used. Therecycled fibres can contain all the above mentioned pulps in addition tofillers, printing inks etc. Chemical pulps, however, are preferred sincethey impart a superior feeling of softness to tissue sheets made fromit. The utilization of recycled fibres for making tissue or fluff oftenincludes a process step known as deinking to remove as much as possibleof the printing ink from the fibre slurry and most of the fillermaterial to get an acceptable brightness of the recycled fibre slurryand paper machine runnability. The deinking process often includesaddition of anionic substances such as saponified fatty acids and waterglass to the fibre slurry. These substances are sometimes carried overto the paper machine and due to the fact that they are anionic, they caninactivate cationic chemicals added to the stock. These substances arecalled anionic detrimental substances or “anionic trash”.

To evaluate the performance of the papermaking process according to theinvention a number of parameters can be measured. To determine thestatic electricity the static potential is measured. The effect of thedebonder system can be determined by measuring knot content, burststrength, defiberization energy and wetting rate. Low burst strength andlow defiberization energy shows that the fibre-to-fibre bonds are weak,which enhances the softness.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the gist and scope of the present invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the claims. The following exampleswill further illustrate how the described invention may be performedwithout limiting the scope of it. If not otherwise stated, all contentsand percentages as described herein refer to weight percent.

EXAMPLE 1

A coconut oil was mixed with a parasubstituted alkyl benzylsulfonic acid(˜C12) (anionic surfactant) and an unsaturated fatty alcohol with 16 to18 carbon atoms being ethoxylated with 5 EO (non-ionic surfactant). Thecontents of the components were 50 wt % oil, 1 wt % anionic surfactant,and 49 wt % non-ionic surfactants. The oil-surfactant blend was thenheated to 50° C. Aqueous solutions with and without a Polyamine BewotenC410 (polymer) were prepared. The concentration of the polymer in theaqueous solution was 4 wt%. The aqueous solutions were heated separatelyto 50° C. The oil-surfactant blend was subsequently emulsified into theaqueous solutions by means of an Ultra-Turrax® (high-shear equipment).The compositions were subsequently cooled to room temperature in a waterbath. The weight ratio of the oil-surfactant blend to the aqueoussolution was 15:85. The compositions prepared will in the following bereferred to as debonder compositions D1 and D2 respectively.

The debonder compositions used in the examples:

D1: Eka Soft F61® composed of 3.4 wt% Polyamine Bewoten C410 and theoil-surfactant blend in aqueous solutionD2: Oil-surfactant blend (Eka Soft F60®) in aqueous solution

The polymer used in the examples:

P1: Polyamine Bewoten C410 (Eka Soft F50®)

The silicious materials used in the examples are:

S1: Silica sol (Eka NP 320®)

S2: Eka Soft F40®, a synthetic hectorite, hydrous Sodium LithiumMagnesium Silicate.S3: Composition containing 51 and S2 in weight ratio 1:1S4: Composition containing 51 and S2 in weight ratio 2:1S5: Composition containing 51 and Bentonite in weight ratio 1:1S6: Composition containing 51 and Bentonite in weight ratio 2:1S7: Composition containing 51 and Bentonite in weight ratio 1:1

The silicious materials, S1-S7, either as sole materials or mixturesthereof, were dissolved in water to form an aqueous solution with 1 wt %silicious material. Mixtures S3-S7 are defined in the schedule below:

Dry weight ratio NP320 Laponite ® Bentonite Comp. Silica:Smectite (8 wt%) (6 wt %) (100 wt %) Water S3 1:1  75 g (1) 100 g (2) — — S4 2:1 150 g(1) 100 g (2) — — S5 1:1 100 g (1) — 8.0 g (3) 92 (2) S6 2:1 100 g (1) —4.0 g (3) 46 (2) S7 1:1 100 g (1) — 8.0 g (2) 92 (3) The numbers inbrackets reflect the addition sequence. The compositions were treatedwith Ultra-turrax for 10 min at 10.000 rpm.

Dry paper sheets were prepared by mixing 15 grams of chemical pinesulphate pulp with water up to 750 ml. If used, the debondercompositions were added to the pulp suspension followed by 10 minutes ofagitation. If used, the silicious materials were added after 8 minutesof agitation. After 10 minutes the formed sheets were prepared in astandard PFI-sheet former (A4 sheets). The sheets were then pressedaccording to standard method SCAN C26:76. Finally, the sheets were driedon a cylinder to about 90-95% dry content and were then conditioned in aclimate room at 23° C. and 50% relative humidity. If the additives weresprayed, 10 ml of the diluted product was used, with a concentrationappropriate to receive a certain dosage level. The spraying was eitherconducted on wet paper web after pressing (about 50% dry content) or ondried and conditioned paper web (about 93% dry content). If sprayed ondried and conditioned paper web, the sheets were dried and conditionedonce again before measurements were made.

EXAMPLE 2

In example 2 the defiberization energy and static potential weremeasured of sheets prepared from different combinations of debondercompositions added to the cellulosic suspension and silicious materialsadded to the sheets. The amount of debonder composition added to thecellulosic suspension was 2.0 kg/ton based on dry cellulosic fibres. Thepolymer (Polyamine Bewoten C410) was added in conjunction with thedebonder composition or separately in an amount of 0.033 kg/ton based ondry cellulosic fibres. From 0 to 2.0 kg silicious material/ton drycellulosic fibres was added to the sheets as set out in table 1. Thedebonder compositions, polymer and silicious materials were added eitherto the furnish (F) or sprayed on the dried and conditioned paper web(about 93 wt % dry content) (S). Dry paper sheets were preparedaccording to example 1. The static potential of the sheets was measuredwith an Electrostatic field measurement device (JCI 148) and a highvoltage head JCI (John Chubb Instrumentation 140) connected to apin-defiberizer. The defiberization is measured in kJ/kg and the staticpotential is measured in kVolt.

TABLE 1 Total dosage of silicious materials Test 0 kg/ton 0.25 kg/ton0.5 kg/ton 1.0 kg/ton 2.0 kg/ton No. Additives (kJ/kg)(kV) (kJ/kg)(kV)(kJ/kg)(kV) (kJ/kg)(kV) (kJ/kg)(kV) 1 None 165 7.0 — — — — — — — — 2Sprayed H₂O 159 6.5 — — — — — — — — 3 P1(F) + D2(S) 80 13.0 — — — — — —— — 4 D1(S) 90 13.0 — — — — — — — — 5 D2(F) + P1(F) + — — 110 10.0 955.0 85 −4.7 — — S2(F) 6 D2(F) + P1(F) + — — 110 10.0 110 8.0 105 1.7 115−6.4 S2(F) + S1(F) 7 D2(F) 155 7.0 — — — — — — — — 8 D2(F) + P1(F) 11512.5 — — — — — — — — 9 D2(F) + P1(S) 125 10.0 — — — — — — — — 10 D2(F) +P1(S) + — — 160 7.6 155 6.5 155 3.3 — — S1(S) 11 D2(F) + P1(F) + — — 1051.4 105 4.0 100 5.5 — — Inv S2(S) 12 D2(F) + P1(F) + — — 115 9.0 115 6.8120 4.0 — — S1(S) 13 D2(F) + P1(F) + — — 100 5.2 110 5.0 110 1.3 — — InvS3(S)

It is evident from the results of Table 1 that a lower static potentialcan be reached more rapidly with a low dosage according to theinvention.

EXAMPLE 3

In example 3 the static potential of sheets was measured for solesilicious materials. From 0 to 2.0 kg silicious material/ton drycellulosic fibres were added as set out in table 2. The siliciousmaterials were added either sprayed on the wet paper web (about 50 wt %dry content) (SWP) or the dried and conditioned paper web (about 93 wt %dry content)(SDP). Dry paper sheets were prepared according toexample 1. The static potential was measured in the same way as inexample 2.

TABLE 2 Dosage of silicious materials 0.125 0.25 0.5 1.0 2.0 Test 0kg/ton kg/ton kg/ton kg/ton kg/ton kg/ton No. Additives (kV) (kV) (kV)(kV) (kV) (kV) 1 S1 (SWP) 7.6  0.4 −5.4 −3.7 −2.2 −0.8 2 S2 (SWP) 7.6−1.4 −3.0 −4.0 −4.3 −6.6 3 S1 (SDP) 7.5  0.7  0.7  0.5 −0.3 −0.5 4 S2(SDP) 7.5 −3.9 −6.9 −8.5 −8.1 −7.3

It is evident from the results of Table 2 that a low static potentialcan be rapidly reached with a low dosage of smectite clay according totests 2 and 4 of the invention.

EXAMPLE 4

In example 4 the static potential of sheets was measured for solesilicious materials and combinations thereof. 0 to 0.5 kg siliciousmaterial/ton dry cellulosic fibres according to table 3 were added. Thesilicious materials were sprayed on the wet paper web (about 50 wt % drycontent). Dry paper sheets were prepared according to example 1. Thestatic potential was measured in the same way as in example 2.

TABLE 3 Dosage of silicious materials 0.125 0.25 0.5 Test 0 kg/tonkg/ton kg/ton kg/ton No. Additives (kV) (kV) (kV) (kV) 1 None 7.0 — — —2 Sprayed H₂O 6.1 — — — 3 S1 — 0.4 −5.4 −3.7 4 S2 — −1.4 −3.0 −4.0 5 S3— — −4.1 −4.6 6 S4 — — 1.1 −3.0 7 S5 — — −0.6 0.7 8 S6 — — −0.1 1.4 9 S7— — 3.5 1.7

It is evident from the results of Table 3 that a low static potentialcan be rapidly reached with a small dosage of Laponite RD® according tothe invention.

EXAMPLE 5

In example 5 the static potential and the defiberization energy of thesheets prepared from a furnish containing a debonder composition andpolymer were measured. The dried and conditioned paper web (about 93 wt% dry content) were prior to measurements also sprayed with Laponite®and Laponite®-starch mixtures. The amount of debonder composition addedto the cellulosic suspension was 2.0 kg/ton based on dry cellulosicfibres and the polymer addition was 0.12 kg/ton based on dry cellulosicfibres. The total amount of silicious material added to the dried andconditioned paper web (about 93 wt % dry content) was varied between0.125 to 1.0 kg silicious material/ton dry cellulosic fibres accordingto table 4. The Laponite®-starch mixture of S2 and OS (oxidised starch,Perfectamyl P 255 SH) was made in a weight ratio of S2 to OS of 1:3. Drypaper sheets were prepared according to example 1.The static potentialand defiberization energy were measured in the same way as in example 2.

TABLE 4 Total dosage of silicious materials Test 0 kg/ton 0.125 kg/ton0.25 kg/ton 0.5 kg/ton 1.0 kg/ton No. Additives (kJ/kg)(kV) (kJ/kg)(kV)(kJ/kg)(kV) (kJ/kg)(kV) (kJ/kg)(kV) 1 D2(F) + P1(F) 120 9.7 — — — — — —— — 2 D2(F) + P1(F) + — — — — 105 6.8 125 6.7 — — S2-OS(S) 3 D2(F) +P1(F) + — — 105 8.0 90 5.0 100 2.0 105 −0.3 S2(S) 4 D2(F) + P1(F) + — —— — — — 110 3.6 — — S3(S)

It is evident from Table 4 that tests 3 and 4 according to the inventionresult in lower static potential and acceptable defiberization energycompared to test 2 in which a laponite-starch mixture was applied to theweb.

1. A process of producing a cellulosic fibre web comprising a) providinga cellulosic suspension b) dewatering the cellulosic suspension andforming a cellulosic fibre web c) applying a smectite clay in an amountfrom about 0.01 to about 2 kg/t dry cellulosic fibres to said cellulosicfibre web, wherein no polymer is added to the formed cellulosic fibreweb.
 2. A process of producing a cellulosic fibre web comprising a)providing a cellulosic suspension and adding a debonder system to thecellulosic suspension b) dewatering the cellulosic suspension andforming a cellulosic fibre web c) applying a smectite clay in an amountfrom about 0.01 to about 2 kg/t dry cellulosic fibres to the formedcellulosic fibre web.
 3. The process according to claim 1, wherein adebonder system is added to the cellulosic suspension.
 4. The processaccording to claim 1, wherein a polymer is added to the cellulosicsuspension.
 5. The process according to claim 1, wherein the smectiteclay is added in an amount from about 0.1 to about 1 kg/ton drycellulosic fibres to the formed web.
 6. The process according to claim1, wherein the smectite clay is sprayed on the web.
 7. The processaccording to claim 2, wherein the debonder system comprises (i) an oil,fat or wax, (ii) at least one non-ionic surfactant, and (iii) at leastone anionic surfactant.
 8. The process according to claim 2, wherein thedebonder system comprises a quaternary ammonium surfactant.
 9. Theprocess according to claim 2, wherein the weight ratio of the debondersystem to smectite clay added to the web ranges from about 1:50 to about100:1.
 10. The process according to claim 2, wherein the smectite clayis laponite and/or bentonite.
 11. The process according to claim 2,wherein the static potential of the cellulosic fibre web is lower than10 kV.
 12. The process according claim 2, wherein the defiberizationenergy of the cellulosic fibre web is lower than 120 kJ/kg.
 13. Theprocess according to claim 2, wherein the cellulosic fibre web isfurther processed to produce air-laid paper, tissue or fluff.
 14. Acellulosic fibre web obtainable by the process as claimed in claim 2.15. A cellulosic fibre web comprising smectite clay in an amount fromabout 0.25 to about 0.75 kg/ton dry cellulosic fibres wherein the staticpotential is lower than 5 kV.
 16. The process according to claim 2,wherein a polymer is added to the cellulosic suspension.
 17. The processaccording to claim 3, wherein the debonder system comprises (i) an oil,fat or wax, (ii) at least one non-ionic surfactant, and (iii) at leastone anionic surfactant.
 18. The process according to claim 2, whereinthe debonder system comprises a quaternary ammonium surfactant.
 19. Theprocess according to claim 3, wherein the weight ratio of the debondersystem to smectite clay added to the web ranges from about 1:50 to about100:1.
 20. The process according to claim 1, wherein the smectite clayis laponite and/or bentonite.